Wow! If it's OSU -3.5pts the wise guys are thinking close game, very close. Your defense is looking better with each and every game. Combine this with a senior QB, a solid running game and 106K screaming fans. Yep -3.5 sounds right.
Opening lines depend on your definition of them...are you talking about BetOnline putting up soft numbers with tiny limits? Or are you talking about a more serious book putting up lines with more playable limits?
This is a good (and free) site for tracking line history at both small (the BOL types) and big (Pinnacle/Bookmaker)...